In European Patent EP 0 175 109 B1, one or two drive pinions mesh with a T-section ring gear rigidly secured to the outside diameter of a drum. Drum flexures can lead to drum distortions, which lead, also in combination with various thermal expansions, to relative displacements and/or inclinations of the tooth flanks with nonuniform face width load behavior, so that the rim gear drive and its transmission of force can be endangered even with hardened tooth flanks. In order to distribute the load transmission in an approximately uniform way over the full face width of the drive teeth and to achieve a somewhat uniform load flank contact pattern, it has heretofore been proposed to use a so-called self-adjusting drive pinion, in which the pinion body is mounted on the pinon shaft with a seat in the form of a spherical cap. Such a pinion mounting can compensate for any alignment errors of the pinion and/or of the rim gear; however, such a pinion is very complicated in design and expensive to manufacture.